State-dependent behaviour in breeding barn swallows (Hirundo rustica): consequences for reproductive effort

K A Spencer, D M Bryant

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)

Abstract

Life-history theory offers an explanation for the intraspecific variation in reproductive effort; increased levels of current reproductive success, for example, may trade off against residual reproductive value. Even where such trade-offs have been demonstrated, however, much variation in effort remains unexplained and the underlying causes are usually obscure. We examined body state, i.e. energy reserves, as a factor, which could moderate reproductive effort. Specifically, overnight heating and cooling treatments were used to adjust dawn energy reserves in female swallows attending their nests without impinging on the opportunities for foraging. Changes in reproductive effort were measured as 'daytime energy expenditure' (doubly labelled water technique) and the 'number of feeding visits' during brood rearing, which both relate positively to current reproductive success. Our experimental treatments and responses were then compared using the common currency of energy. In response to positive and negative state manipulations, female swallows increased and decreased, respectively, their daytime energy expenditure (and number of feeding visits). These responses to experimental manipulation of state provided evidence of a direct link between the energy expenditure, life history and behaviour, which has hitherto proved elusive. They allow that energy supply and expenditure play a regulatory role in reproductive effort, and indicate that units of energy expenditure probably carry fitness costs and benefits, which are context dependent.

Original languageEnglish
Pages (from-to)403-410
Number of pages8
JournalProceedings of the Royal Society of London Series B: Biological Sciences
Volume269
Issue number1489
DOIs
Publication statusPublished - 22 Feb 2002

Keywords

  • body state
  • energy
  • trade-offs
  • reproduction
  • life-history theory
  • DOUBLY-LABELED WATER
  • MARTINS DELICHON-URBICA
  • ENERGY-EXPENDITURE
  • CLUTCH SIZE
  • BROOD SIZE
  • BIRDS
  • COSTS
  • PARENT
  • MASS
  • HIRUNDINIDAE

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